fastapi

FastAPI Skill

High-performance Python web framework.

Ecosystem Graph

graph LR
  fastapi["FastAPI"]
  fastapi -- "alternative to" --> express
  fastapi -- "integrates with" --> openai
  fastapi -- "deploys to" --> docker

Quick Start

FastAPI leverages Python type hints to generate OpenAPI documentation automatically and serialize data incredibly fast using Pydantic.

pip install fastapi uvicorn pydantic

Production Patterns

Dependency Injection

Use the Depends() feature heavily. Inject database sessions, authenticators, and external clients directly into your route functions rather than relying on global state. This makes unit testing trivial by overriding dependencies.

Architecture & Scaling

Async vs Sync

FastAPI handles both def and async def routes. If you are using a synchronous database driver (like psycopg2), declare the route as def so FastAPI runs it in an external threadpool. If using an asynchronous driver (like asyncpg), use async def.

Error Recovery

Raise HTTPException inside your routes for expected errors (e.g., 404). For unexpected global errors, register a global exception handler via @app.exception_handler to sanitize the error response and log the stack trace to Sentry.

Security Notes

Use OAuth2PasswordBearer for built-in token extraction. Never expose raw SQL queries; always use an ORM like SQLAlchemy or SQLModel to prevent SQL injection.

Relationships

Alternatives: express

Works Well With: openai

Deploys To: docker

References

• FastAPI Docs

Why use this skill

Use this when your agent works with fastapi — structured patterns beat pasted docs and prevent common hallucinations.

AI pitfalls

• Using outdated SDK or API versions from training data
• Inventing environment variable names
• Omitting error handling and retry logic

Production checklist

• Secrets in environment variables, not source code
• Error handling and logging in place
• Rate limits and timeouts configured